The present invention relates generally to hollow structures such as rotor blades, fan blades compressor blades and vanes and the like used in gas turbine engines, and more particularly to internally stiffened hollow structures utilizing titanium and titanium composites.
Modern high-thrust/high-bypass gas turbine engines require large fan blades and large compressor blades and vanes, and may operate at high rotation speeds, high compression ratios and high turbine entry temperatures. Consequently, rotating engine components must be strong, stiff, light in weight and high temperature resistant. Conventional structures for fan blades and compressor blades and vanes include hollow titanium structures having internal stiffening ribs or honeycomb structures disposed in the hollow space within the structures. The stiffening ribs may be machined into the inner surfaces of two bonded segments that comprise such a structure, or the honeycomb may be inserted into the hollow space prior to bonding. The stiffening ribs are expensive and difficult to manufacture. The resultant structure is usually light in weight but characterized by inherent relatively low stiffness.
In accordance with the teachings of the invention, a hollow component such as a turbine engine blade or vane may be stiffened internally by bonding a layer of titanium matrix composite onto the inner (usually curved) surfaces of the structural segments comprising the component. The layer may comprise one or more mats of ceramic fibers and alloy matrix which form a stiffening layer of titanium matrix composite on the inner surfaces of the structure. The composite may be applied using methods such as vacuum hot pressing or hot isostatic pressing of alloy foils and fibers, or by plasma spray deposition of molten alloy powder over fiber mats. Such reinforced segments are then joined by any suitable method such as brazing, diffusion bonding or electron beam welding to form the desired hollow structure. Because of the high specific stiffness of the composite layers, and the location of the layers at the outermost extremities of the cavity defined within the structure, the resultant structure has high stiffness and is light in weight.
The invention has wide application to high-bypass gas turbine engines such as those presently used on commercial and military aircraft, and to future engine generations having high bypass ratios, compression ratios and speeds of rotation.
It is therefore a principal object of the invention to provide an improved stiffened structure for a rotor blade, fan blade, or compressor blade or vane for a gas turbine engine.
It is a further object of the invention to provide a stiffened hollow blade or vane structure comprising titanium for use in a rotor, compressor or fan within a gas turbine engine.
These and other objects of the invention will become apparent as a detailed description of representative embodiments proceeds.